We used a range of computational techniques to reveal an increased histamine affinity for its H₂ receptor upon deuteration, which was interpreted through altered hydrogen bonding interactions within the receptor and the aqueous environment preceding the binding. Molecular docking identified the area between third and fifth transmembrane α-helices as the likely binding pocket for several histamine poses, with the most favorable binding energy of −7.4 kcal mol⁻¹ closely matching the experimental value of −5.9 kcal mol⁻¹. The subsequent molecular dynamics simulation and MM-GBSA analysis recognized Asp98 as the most dominant residue, accounting for 40% of the total binding energy, established through a persistent hydrogen bonding with the histamine −NH₃⁺ group, the latter further held in place through the N–H∙∙∙O hydrogen bonding with Tyr250. Unlike earlier literature proposals, the important role of Thr190 is not evident in hydrogen bonds through its −OH group, but rather in the C–H∙∙∙π contacts with the imidazole ring, while its former moiety is constantly engaged in the hydrogen bonding with Asp186. Lastly, quantum-chemical calculations within the receptor cluster model and utilizing the empirical quantization of the ionizable X–H bonds (X = N, O, S), supported the deuteration-induced affinity increase, with the calculated difference in the binding free energy of −0.85 kcal mol⁻¹, being in excellent agreement with an experimental value of −0.75 kcal mol⁻¹, thus confirming the relevance of hydrogen bonding for the H₂ receptor activation.

A new synthetic strategy involving the Pinner reaction offers various amidino-functionalized 2-substituted benzoxazolesviaamidino-substituted 2-aminophenols with sub-micromolar antiproliferative activities.

We present the synthesis of a range of benzimidazole/benzothiazole-2-carboxamides with a variable number of methoxy and hydroxy groups, substituted with nitro, amino, or amino protonated moieties, which were evaluated for their antiproliferative activity in vitro and the antioxidant capacity. Antiproliferative features were tested on three human cancer cells, while the antioxidative activity was measured using 1,1-diphenyl-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing antioxidant power (FRAP) assays. Trimethoxy substituted benzimidazole-2-carboxamide 8 showed the most promising antiproliferative activity (IC₅₀ = 0.6–2.0 µM), while trihydroxy substituted benzothiazole-2-carboxamide 29 was identified as the most promising antioxidant, being significantly more potent than the reference butylated hydroxytoluene BHT in both assays. Moreover, the latter also displays antioxidative activity in tumor cells. The measured antioxidative capacities were rationalized through density functional theory (DFT) calculations, showing that 29 owes its activity to the formation of two [O•∙∙∙H–O] hydrogen bonds in the formed radical. Systems 8 and 29 were both chosen as lead compounds for further optimization of the benzazole-2-carboxamide scaffold in order to develop more efficient antioxidants and/or systems with the antiproliferative activity.

Nicotinamide adenine dinucleotide (NAD) coenzyme is a vital part of numerous enzymatic reactions that are involved in all major biological processes from energy metabolism to cell survival. Accordingly, it is used in a great number of biocatalytic reactions, as analytical biosensors, and in test kits for diagnostic and analytical purposes. This coenzyme is unstable in aqueous solutions, meaning that the minimization of its degradation during storage, assays, and enzyme-catalysed oxidoreductive reactions is of high importance. Herein, we report on the stabilisation of NAD (NAD⁺ as oxidised, and NADH as its reduced form) by deep eutectic solvents (DES), an emerging class of solvents that offer numerous remarkable advantages such as high tunability, and capability to stabilise a wide range of commercially important compounds of natural origin. Preliminary DES screening revealed that out of 7 candidates, choline chloride:urea (ChCl:U) shows the best ability to stabilise both NAD forms. Computational analysis (quantum chemical calculations and molecular dynamics simulations) provided a deeper insight into possible mechanisms behind the observed stabilisation, by identifying geometries and the solvation structure of NAD coenzymes in these solvents, and analysing their possible degradation pathways. Finally, prolonged NAD stability (up to 50 days) in ChCl:U is detected and the system is further confirmed as a stable working NAD solution in a model enzymatic assay.